In medical applications, an aspiration device is one which applies pressure or partial vacuum to draw a fluid or sample into a syringe or into an attached needle lumen. Such devices are also useful for securing specimens from palpable and non-palpable lesions found in the thyroid, breast, lymph nodes, prostate, liver, kidney, lung and pancreas for histologic and cytologic examination.
The simplest and most widely used prior art aspirating device is a conventional, plastic hypodermic syringe of the type having a hollow needle opening into a syringe barrel and a plunger for varying the volume and pressure inside the barrel. In use, negative pressure is created by drawing back on the plunger. This requires two hands, one to hold the syringe barrel and one to withdraw the plunger, or, if the syringe incorporates finger and thumb rings, negative pressure is generated by the thumb flexing in opposition to the fingers.
In certain other procedures, thoracentesis for example, it is imperative that the tip of the needle be precisely located within the pleural space but not so deeply inserted as to cause puncture to the lung. Briefly, the aspiration needle is connected to a syringe, insuring that the plunger is fully inserted into the barrel of the syringe. The needle is inserted into the body and slowly advanced toward the pleural space. During this advancement, two hands are required to effect precise location of the needle tip within the pleural space. The syringe and needle are advanced into the body with one hand, while simultaneously pulling back on the syringe plunger with the other hand to create a vacuum within the syringe barrel and inside the needle. Entry of the needle into the pleural space is manifest by the pleural effusion flowing back into the syringe.
Accordingly, there is a need for an improved single-hand operated aspiration device for conducting medical procedures involving aspiration of bodily fluids. One object of the invention is to eliminate the necessity of manually aspirating the syringe so that both hands may be dedicated to the correct placement of the needle tip.
It is another object of the invention to provide a plastic syringe which has highly sensitive feel and low resistance, while at the same time offering the advantage of improved single-hand operation during aspiration procedures.